1. Field of the Invention
Aspects of the present invention relate to a transfer unit and an image forming apparatus employing the same.
2. Description of the Related Art
In general, a color image forming apparatus forms toner images of various colors on a plurality of image supports and superimposes the toner images on a printing medium using a transfer unit. A transfer unit typically includes an intermediate transfer body. The toner images are transferred from the plurality of image supports onto the intermediate transfer body, such that the toner images are overlapped to form a color image. A transfer member transfers the color image from the intermediate transfer body to the printing medium.
A high voltage is applied to the intermediate transfer body and the transfer member, and thus, the printing medium passing there through is electrified at a certain electric potential. The electrified printing medium may be attracted to the intermediate transfer body, after passing through the intermediate transfer body and the transfer member. Thus, there is a need to de-electrify the printing medium, to prevent the printing medium from being attracted to the intermediate transfer body.
To this end, a method for de-electrifying a printing medium, by applying a corona discharge to an electrified printing medium, has been developed. However, generating the corona discharge creates ozone, thereby causing an environmental problem. Such an image forming apparatus requires additional devices, such as, an ozone filter, a duct, and a fan, etc., to remove the ozone, thereby increasing manufacturing cost and lowering manufacturing efficiency.
As another method for de-electrifying a printing medium, an image forming apparatus including a grounded de-electrifying member, which is disposed adjacent to a printing medium, has been provided. This method is relatively effective, if an intermediate transfer body of the apparatus has a diameter of 40 mm or less. However, if the intermediate transfer body has a diameter larger than 40 mm, the de-electrification of the printing medium is insufficient, and thus, the printing medium may be attracted to the intermediate transfer body.